2Yrs Unsolved Binding/Knocking Suspension During Sharp Turns

[Wunderground]

Greetings!

I've been a member here for a few years, but spent most of that time scouring the threads for similar issues.

I'll try and keep this concise so that no one has to read through paragraphs to get info.

Vehicle:
- 2002 Yukon XL Denali
- 6.0L V8
- AWD
- 327,000kms (203,000mi)

Symptom:
- Binding/Knocking during sharp turns
- At steering wheel lock, the truck's front end almost seems to jump like it's skipping teeth on a gear.
- Happens in both Drive and Reverse
- Faint whining sound during slow sharp turns (almost hydraulic in sound)

Repeatable?: (i.e. can I replicate the issue on demand?)
- Yes

Conditions: (i.e. when does it happen?)
- Vehicle is at operating temperature
- My defacto standard for replicating involves a routine 75km (46mi) commute, whereby upon arrival to the destination, as soon as I pull into a standard parking lot spot, the truck exhibits binding/knocking like a knuckle is skipping.
- Same binding/knocking happens after a considerable amount of driving/parking (e.g. while running errands)

Troubleshooting: (what have I tried)
- Wheel Bearing replacement - I don't think it is related, but I needed new bearings at the same time I noticed the issue.
- Transmission shop examined Transfer Case - Issue persisted
- Dealership performed "Rear Diff Service" (all fluids changed) - Issue persisted
- New tires (while this was more of standard maintenance and not for troubleshooting... - Issue persisted
- Transmission shop (pt. 2) Recommended alignment. This almost had me convinced that it was the culprit, but... - Issue persisted
- Replaced shocks. Air ride conversion to conventional shocks. Rides better but... - Issue persisted

Notes:
The truck still pulls strong on the highway, no suspicious engine sounds. For all intents and purposes, the truck is fine except for this knocking sound.
Issue appears to be dependent on the vehicle being at operating temp.
The 75km commute is by far my standard troubleshooting after some work has been performed.

While I can do standard maintenance, I'm not a mechanic, and not familiar with any other component failure that could result in this issue. Steering? Bushings?

Any help is appreciated.

Thanks!

 

[afpj]

Is your entire drivetrain original? Did the dealership check front suspension components? Has anyone done front differential fluid change and what was the condition of the fluid coming out for both front or rear differentials? Same question for the transfer case.

 

[Wunderground]

Note: I took over the vehicle from my father, and unformtunately, he didn't keep up with scheduled maintenance.

Yes, Drivetrain is all original. Dealer inspected front suspension. No issues were reported.

Front and Rear Diff as well as Transfer Case fluids were changed within a two week time period. Since it was long overdue, the fluid was in rough shape, i.e. burnt. According to the dealer, there was no damage (which I find hard to believe), although a flush was required for the rear (not sure what that entails).

My concern has always been that permanent damage has been done to either or both of the diffs.

 

[Bill 1960]

Usually my first suspect would be a worn front CV, it’s a classic symptom. However, those typically exhibit regardless of temperature and are easy to diagnose for any competent mechanic.

Suspect number 2, and particularly because it is temperature related, will be the viscous coupler in the transfer case. That’s a fluid filled clutch that allows a limited amount of wheel speed differential front to rear in turns. If it seizes up, the vehicle will buck in turns on hard surfaces just like a conventional 4x4.

 

[swathdiver]

Greetings!

I've been a member here for a few years, but spent most of that time scouring the threads for similar issues.

I'll try and keep this concise so that no one has to read through paragraphs to get info.

Vehicle:
- 2002 Yukon XL Denali
- 6.0L V8
- AWD
- 327,000kms (203,000mi)

Symptom:
- Binding/Knocking during sharp turns
- At steering wheel lock, the truck's front end almost seems to jump like it's skipping teeth on a gear.
- Happens in both Drive and Reverse
- Faint whining sound during slow sharp turns (almost hydraulic in sound)

Repeatable?: (i.e. can I replicate the issue on demand?)
- Yes

Conditions: (i.e. when does it happen?)
- Vehicle is at operating temperature
- My defacto standard for replicating involves a routine 75km (46mi) commute, whereby upon arrival to the destination, as soon as I pull into a standard parking lot spot, the truck exhibits binding/knocking like a knuckle is skipping.
- Same binding/knocking happens after a considerable amount of driving/parking (e.g. while running errands)

Troubleshooting: (what have I tried)
- Wheel Bearing replacement - I don't think it is related, but I needed new bearings at the same time I noticed the issue.
- Transmission shop examined Transfer Case - Issue persisted
- Dealership performed "Rear Diff Service" (all fluids changed) - Issue persisted
- New tires (while this was more of standard maintenance and not for troubleshooting... - Issue persisted
- Transmission shop (pt. 2) Recommended alignment. This almost had me convinced that it was the culprit, but... - Issue persisted
- Replaced shocks. Air ride conversion to conventional shocks. Rides better but... - Issue persisted

Notes:
The truck still pulls strong on the highway, no suspicious engine sounds. For all intents and purposes, the truck is fine except for this knocking sound.
Issue appears to be dependent on the vehicle being at operating temp.
The 75km commute is by far my standard troubleshooting after some work has been performed.

While I can do standard maintenance, I'm not a mechanic, and not familiar with any other component failure that could result in this issue. Steering? Bushings?

Any help is appreciated.

Thanks!

I would say it's time to look inside your transfer case. The AWD case is what is supposed to keep the front wheels from binding and skipping in turns unlike those of us with 4x4s. The AWD case has a planetary inside, like a rear differential, so the front wheels can slip, and yours isn't being allowed to slip as it should.

When did you last change the transfer case fluid and was it the right fluid? Did you do it or a shop? If memory serves, yours does NOT take transmission fluid, it takes a special Autotrac fluid. As fellas get to work and sit down with a cup of joe, they'll start chiming in.

 

[Wunderground]

@Bill 1960 and @swathdiver., thanks for the feedback!

I really think the transmission shop that inspected the transfer case didn't do deep inspection. I'm thinking I should source a VC and replace it, and report back here.

Is this the right play?

 

[swathdiver]

@Bill 1960 and @swathdiver., thanks for the feedback!

I really think the transmission shop that inspected the transfer case didn't do deep inspection. I'm thinking I should source a VC and replace it, and report back here.

Is this the right play?

Well, if yours were mine I'd exhaust all the cheap options first, starting with checking the fluid level and seeing what color/condition it is in. Don't jump to the worst case scenario like I do! LOL I heard a tick earlier this year and thought it was time for a new engine, my wife could see the gray hairs growing on my head! Turned out to be a bad exhaust gasket.

 

[Bill 1960]

I almost never replace a part without a definitive diagnostic test. In your shoes, I would pay the dealer or a trusted quality shop to run the diagnostic procedures outlined in the factory service manual. An “inspection “ won’t cut it.

Also at that mileage, I would not even open the case on the TC unless I was prepared for a total rebuild. Considering the labor involved just to R&R vs. the modest cost of a rebuild kit.
However, it doesn’t sound like it’s in your wheelhouse to DIY that. And most shops do not want to rebuild a TC anymore either. Generally the go-to repair is source another TC and just change it. Either from a salvage yard, a remanufacturer, or good old GM on the high $ end.

The one thing you can pray for is that someone put the wrong fluid in it as @swathdiver brought up. Definitely worth looking into.

 

[Wunderground]

Sounds reasonable to start with a fluid change for the TC. The holidays have already drained most of my budget.

Is there a specific identifier that will tell me what type of TC is on the vehicle, so I can specify the correct fluid? I know shops can source this kind of thing, but I suppose it's for my own piece of mind so I know what to expect when the mechanic tells me.

 

[Scottydoggs]

ive seen this before, but in a ford exploder, the speed sensor on the t case was bad.

 

[swathdiver]

Sounds reasonable to start with a fluid change for the TC. The holidays have already drained most of my budget.

Is there a specific identifier that will tell me what type of TC is on the vehicle, so I can specify the correct fluid? I know shops can source this kind of thing, but I suppose it's for my own piece of mind so I know what to expect when the mechanic tells me.

Transmission fluid is red, the Autotrac fluid is kinda blue. It's called Auto Track fluid and the original part number is: 12378396

 

[Fless]

Transmission fluid is red, the Autotrac fluid is kinda blue. It's called Auto Track fluid and the original part number is: 12378396

Does the AWD transfer case take Auto Trac II fluid? I thought that it takes transmission fluid. @Rocket Man

 

[swathdiver]

Does the AWD transfer case take Auto Trac II fluid? I thought that it takes transmission fluid. @Rocket Man

I went poking around in different owner's manuals and came up with that. I have been known to be wrong once in a while! LOL

 

[Fless]

You're busted, @swathdiver!

From the horse's mouth: (obviously newer compatible Dexron fluid should be used)

 

[THarber]

I'd re-exam both front hubs as well as upper and lower ball joints.

Tim

 

[swathdiver]

You're busted, @swathdiver!

From the horse's mouth: (obviously newer compatible Dexron fluid should be used)

View attachment 357912

But wait! There's more:

That page is from a 2000 GMC Yukon owner's manual. I went with this because it says, "Automatic Transfer Case".

Ok, so which is right?

 

[Bill 1960]

GM has created a confusing mess of terminology and branding on this topic.

Automatic 4wd is not the same as AWD.

I have the NP246 “Autotrac” transfer case with auto four wheel drive. But it doesn’t use “Auto-trak” transfer case fluid, it specifies Dexron 6 in my manual. I have seen other contradictory information elsewhere.

2008 Tahoe manual (Auto 4x4 the only option):


The AWD TC with full time AWD and the viscous coupler is a different item.

YMMV I’m sure they changed the spec over time.

For the OP; just check your manual, which is available online from GM if you don’t have the original.

 

[rockola1971]

Yup Auto Tcase is not the same as a AWD Tcase when it comes to the fluid used. I also believe somewhere in 2006 or so that the AWD Tcase fluid spec changed because of a different model AWD Tcase?
The Auto Tcase relies on the autotrac fluid for its clutches for the the "auto 4wd" feature. Put Tranny fluid in there and it wont end well for the Tcase.

 

[Wunderground]

This is really good information folks! Thanks for the response.

Since there was little regular maintenance performed before I owned the truck, I've scheduled it at the shop on Monday (Dec. 20th) for a TC fluid change.

I'll report back afterwards.

As for the fluid referenced in my manual? It states "DEXRON -III Automatic Transmission Fluid."

 

[Fless]

This is really good information folks! Thanks for the response.

Since there was little regular maintenance performed before I owned the truck, I've scheduled it at the shop on Monday (Dec. 20th) for a TC fluid change.

I'll report back afterwards.

As for the fluid referenced in my manual? It states "DEXRON -III Automatic Transmission Fluid."

Yes; I posted the page from the OP's 2002 Denali manual. Context matters.